Bokan Mountain and Dora Bay Rare Earth Element Deposits, Prince of Wales Island, Alexander Terrane, Southeast Alaska Completed

Sources/Usage: Public Domain.

Scientific Issue and Relevance

Global demand for critical mineral commodities is on the rise with increasing applications in consumer products, computers, automobiles, aircraft, and other advanced technology products. Much of this demand growth is driven by new technologies that increase energy efficiency and decrease reliance on fossil fuels. The USGS Minerals Program seeks to understand the nature and distribution of critical mineral resources in the United States. In the Alaskan Alexander terrane, both the Early Jurassic Bokan Mountain and Dora Bay igneous complexes are composed of peralkaline granitic rocks with silicate vein dikes enriched in both light and heavy rare earth elements. Both igneous complexes are under study to increase understanding of the nature and distribution of rare earth element (REE) resources in the United States.

Science Activities

We sought to fully characterize the Dotson Zone heavy-rare earth element (HREE) enriched deposit at Bokan Mountain, Alaska, and place the igneous-hydrothermal evolution of the deposit into the context of the petrogenetic evolution of the Bokan Mountain peralkaline granite and other associated uranium-thorium-rare earth element (U-Th-REE) prospects. Parallel characterization and comparison of a less well-mineralized HREE analogue at Dora Bay provided a better understanding of the factors leading to HREE enrichment in peralkaline granites.

Our activities focused on the following:

• Mineralogy, fluid chemistry, and geochronology of the Dotson Zone heavy rare earth elements (HREE),
• Geology and economic geology of the Bokan Mountain intrusion, and
• Mineralogy, geochemistry, and geochronology of the Dora Bay peralkaline intrusion and comparisons to Bokan Mountain.

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